1. Field of the Invention
The present invention relates to a manufacturing method for a field-effect transistor, a manufacturing method for a semiconductor device, and an apparatus therefor.
2. Description of the Related Art
Recently, with the progression of high integration of semiconductor integrated circuits, there has also been required higher miniaturization of semiconductor devices such as a field effect transistor. However, the reliability of the devices must not be deteriorated due to the miniaturization, so both of high miniaturization and high reliability should be realized in such devices.
Particularly, as for a gate insulating film, which is an important structural component of a field effect transistor, such as a MOS transistor, a high dielectric film with a high dielectric constant is being used in place of the conventional silicon oxide film in order to ensure a withstand voltage against the thin thickness of the film. However, when the high dielectric film is directly formed on the silicon substrate, the quality of gate insulating film is decreased to cause an increase in a leak current and a reduction in mobility close to the interface between the silicon substrate and the insulating film. For this reason, as a method for forming the gate insulating film, there has been employed a method in which a thin silicon oxide film is formed on the substrate and the high dielectric film is formed thereon.
If the thickness of silicon oxide film that constitutes two-layered film is too large, the total thickness of the gate insulating film is also large, and this does not meet the requirement of miniaturization. On the other hand, if the thickness of the silicon oxide film is too small, the amount of the leak current increases. For this reason, control of the thickness of silicon oxide film is very important. In recent years, there has been needed an extremely thin oxide film with several angstrom (thickness corresponding to several atomic layers) for miniaturization.
However, the reliability of thin-film measurement by the ellipsometry, which is conventionally used to measure the film thickness, is about over ten angstrom, and the thickness, which is smaller than this value, cannot be accurately measured.
As a method for measuring the thickness of thin film of several atomic layers, RDS (Reflectance Difference Spectroscopy) has been known, and U.S. Pat. No. 4,931,132, which is incorporated herein by reference in its entirety, describes the method of measuring the thickness of crystal growth on the surface of GaAs crystal using this technique. According to this measuring method, in the case of measuring a thickness of a film in which a new atomic layer is formed on the atomic layer already formed as in epitaxial growth, the film thickness is measurable in the atomic layer level since the new atomic layer is formed on a surface to be measured.
However, in general, the gate oxide film is formed by the thermal oxidation and the formation of a film grows toward the inside of the silicon substrate from the surface thereof, and no observable change occurs on the surface. For this reason, it is difficult to carry out such measurement by the same method.
In such a background, the inventors of the present invention made endeavor wholeheartedly this time. Then, we found it possible to observe the state in which the formation of atomic layer grows toward the inside of the silicon substrate by the use of the reflectance difference spectroscopy, and to control the formation of silicon oxide film in order of an atomic layer based on the observed data.
Accordingly, it is an object of the present invention is to provide a field-effect transistor manufacturing method that is capable of controlling a film formation in order of atomic layer using the aforementioned reflectance difference spectroscopy, a semiconductor device manufacturing method, and its device.
In order to attain the above object, according to a first aspect of the present invention, there is provided a manufacture method for a field-effect transistor comprising steps of heating a semiconductor substrate in a predetermined gas atmosphere to advance a reaction between said gas atmosphere and said semiconductor substrate inwardly from a surface of said semiconductor substrate such that an insulating film formed by said reaction grows from the surface of said semiconductor substrate toward an inside of said semiconductor substrate; irradiating light upon the surface of said semiconductor substrate during said heating step and detecting intensity of polarization components in two directions perpendicular to each other of light reflected from an interface between said semiconductor substrate and said grown insulating film, to obtain a thickness of said insulating film in a unit of atomic layer based on a change in the detected intensity; detecting an end point of said reaction based on the film thickness obtained in said irradiating step to terminate said heating step; forming a dielectric film, having a dielectric constant higher than said insulating film, on said insulating film; and forming a gate electrode on said dielectric film.
In order to attain the above object, according to a second aspect of the present invention, there is provided a manufacturing apparatus for a semiconductor device comprising steps of: advancing a reaction toward an inside of a target to form a film in a surface area of said target; irradiating light upon the surface area of said target; detecting intensity of polarization components in two directions perpendicular to each other of the irradiated light which is reflected from the surface of said target; obtaining a thickness of said film formed in said reaction based on a change in the intensity of polarization components of said reflected light detected; and controlling said reaction based on the film thickness obtained.
In order to attain the above object, according to a second aspect of the present invention, there is provided a manufacturing apparatus for a semiconductor device comprising: a process chamber for thermally processing a target in atmosphere including a predetermined gas; an optical apparatus for irradiating light upon said target provided in said process chamber, measuring intensity of polarization components in two directions perpendicular to each other of light reflected from said target, and outputting a measurement signal; and a controller, which is connected to said process chamber and said optical apparatus, for starting a thermal processing to form a film in said target in said process chamber in atmosphere including said predetermined gas, obtaining a thickness of said film formed during said thermal processing based on the measurement signal from said optical apparatus, and terminating said thermal processing if the thickness of said film reaches a predetermined value.